This application is based on and claims priority under 35 U.S.C. xc2xa7 119 with respect to Japanese Application No. 11-359208 filed on Dec. 17, 1999, the entire content of which is incorporated herein by reference.
This invention generally relates to a vehicle seat apparatus. More particularly, the present invention pertains to a seat slide apparatus for a vehicle having a combination of steel and light metal rails.
Known vehicle seat slide apparatus are basically composed of a lower rail fixed to the vehicle floor, an upper rail which holds the seat to slidably move the seat in the vehicle longitudinal direction relative to the lower rail, and a lock mechanism for effecting engagement and disengagement of the lower and upper rails for adjusting the seat position. The seat slide apparatus should be light in weight and the sliding resistance of the upper rails relative to the lower rail should be relatively small. For this reason, the rails are made from lightweight metal alloy such as by aluminum alloy extrusion forming, and rollers or balls are positioned between the sliding surfaces of the rails to reduce frictional resistance.
However, an undesirably large number of components is required to produce these types of seat sliding apparatus because balls or rollers are required as well as a mechanism for supporting the balls or rollers. In addition, the shape of the rail must be relatively accurately dimensioned, especially at the ball or roller holding portion. However, it is difficult to maintain desired dimensions within a tolerance range using an extrusion forming method.
One proposal for addressing some of the disadvantages and drawbacks associated with the construction of known seat sliding apparatus is described in Japanese Utility Model Published Application No. Hei 6(1994)-74465. This seat slide apparatus is composed of a lower rail made of steel, an upper rail comprised of a sliding portion made of aluminum alloy and a seat support portion made of steel, and a lock mechanism engageable with a hole in the lower rail and supported on the seat support portion. The lower portion of the sliding member of this apparatus possesses an H-shaped cross-section having sufficient wall thickness. The apparatus is designed to prevent excessive play of both rails and smoothly slide the upper rail relative to the lower rail by contacting parts of both the upper portions and the outer surface of the vertical portions of the H-shaped part with the inner wall surface of the hollow portion of the lower rail.
So long as the dimensions of the two rails are kept within a small dimensional tolerance, this construction of the seat sliding apparatus reduces the number of components, such as the balls or rollers, without causing sticking during the sliding movement of the upper rail relative to the lower rail due to the contact between the different materials such as steel material and aluminum alloy material, However, this construction of the seat sliding apparatus requires high accuracy forming for the rails. Even a slight deviation from the tolerance causes an excessive play between both rails, thus increasing the sliding resistance.
In light of the foregoing, a need exists for a seat sliding apparatus that is not as susceptible to the disadvantages and drawbacks identified above.
A need exists for a seat slide apparatus which utilizes a different technological solution to produce an improved seat slide apparatus.
According to the present invention, the seat slide apparatus is designed so that a portion of the steel upper rail contacts the inner wall of the hollow portion of the lower rail by using a spring force. It is preferable to provide a surface portion having indented and projecting portions (grooves and ridges) on the inner wall of the hollow portion of the lower rail. A portion of the upper rail is elastically in contact with the surface portion having the projections.
The dimensional tolerance range of the upper rail and the lower rail can be wider by utilizing the elastic characteristics of the upper rail and without causing excessive play of the upper rail during sliding motion relative to the lower rail. In addition, the sliding resistance is kept constant and the assembly work is easier to carry out.
Thus, according to one aspect of the invention, a seat slide apparatus includes a lower rail made from light metal alloy materials having a pair of side portions upwardly extending from both ends of the base portion, with each surface of the inner wall of the side portion having a projection portion. An upper rail made from steel material has flange portions upwardly extending from both ends of a horizontal bottom portion, and each flange portion elastically contacts the projection portions.
According to another aspect of the invention, a vehicle seat slide apparatus includes a lower rail, an upper rail and a lock mechanism. The lower rail is adapted to be secured to the floor of the vehicle and includes a base portion and a pair of side portions. Each of the side portions extends upwardly from one end of the base portion and possesses an inwardly inclined portion. A plurality of projections extend from the inner wall surface of each inclined portion. The upper rail includes a horizontal bottom portion and a pair of flange portions extending upwardly from ends of the horizontal bottom portion. Each flange portion faces one of the inclined portions of the side portion of the lower rail, and each of the flange portions of the upper rail is in contact with the projections of one of the inclined portions. The lock mechanism is engageable with a portion of the lower rail and the upper rail to fix the position of the upper rail with respect to the lower rail.
According to another aspect of the invention, a seat slide apparatus for a vehicle includes a lower rail adapted to be secured to the vehicle floor, an upper rail and a lock mechanism. The lower rail includes a base portion and a pair of side portions, with each of the side portions extending upwardly from one end of the base portion. The upper rail includes a horizontal bottom portion and a pair of flange portions extending upwardly from ends of the horizontal bottom portion. Each flange portion includes a surface portion facing a surface portion of the side portion. A plurality of projections extend away from either the surface portion of each side wall or the surface portion of each flange, and the other of the surface portion of each side wall and the surface portion of each flange contacts the projections. The lock mechanism is adapted to engage a portion of the lower rail and the upper rail to fix the position of the upper rail with respect to the lower rail.